1. Field of the Invention
The invention relates generally to the field of electron beam etching devices, and more particularly to X/Y coordinate positioning mechanisms for the electron beam's stage.
2. Brief Description of the Prior Art
A major problem occurring in drive mechanisms and instrumentation for cross-axis (X/Y) tables or slides is that the "carried" axis usually has to support its own drive mechanism and instrumentation. The drive mechanism and instrumentation is not then mechanically secured to ground and cables have to drag. The slide inertias of the two axes do not match.
In the case of a vacuum contained cross-axis table or stage, the problem is even more serious because the "carried" drive mechanism and instrumentation is mounted in a high vacuum environment. This is usually an intolerable situation due to the lack of materials which can operate with low friction in vacuum environments.
In electron beam processing of integrated circuit chips or masks, high throughput can be achieved if there is a chain of equipment processing the "material" directly through the evacuated chamber. It is not advantageous to have a process mechanism admit raw (unprocessed) "materials" through one port and remove them through the same port. It is desirable that the system allow the processed material to exit on the opposite side of the chamber through another port. This allows loading and unloading to take place in parallel.
Presently, most X/Y stage drives extend, all or in part, through two orthogonal sides of the evacuated chamber. As a result, it is difficult to design apparatus to load the unprocessed material from one side of the chamber and unload it from the other.
Further, present X/Y stages customarily employ ball bearing and race combinations at the interface between stages. However, incorporation of these bearing devices in a high vacuum environment is not desirable because the number of materials that can meet the requirements for bearing purposes and also be high vacuum compatible and magnetically unsusceptible for electron beam purposes are very small and expensive.